1. Technical Field
The present disclosure relates to a method for forcibly charging a high-voltage battery using a motor and a hybrid starter generator (HSG), and more particularly, to a method for forcibly to charge the high-voltage battery with increased or maximum charging power using a motor and a HSG simultaneously in a plug-in hybrid electric vehicle (PHEV) when a vehicle is driven in a forced charging mode of the high-voltage battery.
2. Discussion of the Related Art
A hybrid electric vehicle is an environmentally-friendly vehicle that uses a motor and an engine as a power source to reduce exhaust gas usage and improve fuel efficiency. The hybrid electric vehicle includes a powertrain system configured to separately deliver power from the engine or the motor to wheels or to deliver power from both the engine and the motor to the wheels. The powertrain system for hybrid electric vehicles includes, as shown in FIG. 7, may include an engine 10 and a motor 12 arranged in series, an engine clutch 13 disposed between the engine 10 and the motor 12 to transfer or block engine power, an automatic transmission 14 configured to shift and output motor and/or engine power to wheels, a Hybrid Starter Generator (HSG) 16 connected to a crank pulley of the engine 10 and configured to start the engine 10 or to generate electricity, an inverter 18 configured to operate the motor or to generate electricity, and a high-voltage battery 20 chargeably or dischargeably connected to the inverter 18 to provide power to the motor 12.
A PHEV with the structure described above has a forced charging function for forcibly charging a high-voltage battery while driving when a user presses a “high-voltage battery forced charging mode” button, and while driving in an EV driving mode (e.g., a mode of operating a motor without operating an engine) for a predetermined time period after the forced charging is completed, to forcibly charge the high-voltage battery and improve fuel efficiency.
FIG. 1 is an exemplary flowchart illustrating a method of forcibly charging a high-voltage battery according to the related art. The method may be performed by forced electricity generation according to motor-only operation. First, a driver engages a switch for forcibly charging a high-voltage battery, in operation S101. Successively, the speed and temperature of a motor are sensed in operation S102, and charging power for charging the high-voltage battery using the motor is calculated in operation S103.
The charging power may be determined to be less than maximum power when the temperature and speed of the motor are not considered. The sensed current temperature of the motor may be compared to an operating power limiting temperature for motor operation, in operation S104. When the current temperature of the motor is greater than the operating power limiting temperature, the power of the motor for forcibly charging the high-voltage battery is limited in operation S105, and when the current temperature of the motor is less than or equal to the operating power limiting temperature, the power of the motor for forcibly charging the high-voltage battery is not limited in operation S106. When the power of the motor is not limited, the high-voltage battery is forcibly charged according to operation of the motor. A current state of charge (SOC) of the high-voltage battery is compared to a target SOC in operation S107. When the current SOC of the high-voltage battery exceeds the target SOC, the forced charging terminates in operation S108.
The vehicle is driven in an EV driving mode by motor-only operation, in operation S109, and during driving, the current temperature of the motor is again compared to the operating power limiting temperature of the motor in operation S110. When the current operation temperature of the motor is greater than the operating power limiting temperature, the process proceeds to operation S111 of limiting power of the motor after forced charging terminates. When the power of the motor is limited, the vehicle is driven in a HEV driving mode by starting the engine, in operation S112. Meanwhile, when the current temperature of the motor is less than or equal to the operating power limiting temperature, the EV driving mode is maintained since power of the motor is not limited even after forced charging terminates, in operation S113.
However, the method of forcibly charging the high-voltage battery according to the related art has the following problems. First, since forced charging is performed by motor-only operation, charging power and charging speed with respect to the high-voltage battery may be relatively low, which may disable rapid forced charging. Second, when the temperature of the motor is determined as an excessive temperature, forced charging of the high-voltage battery may be disabled due to power limitation of the motor. Third, since the speed and temperature of the motor are not considered during forced charging of the high-voltage battery, it may not be possible to maximally increase an amount of charging over time. Fourth, since the engine starts due to power limitation of the motor when the temperature of the motor is determined to be an excessive temperature after forced charging is completed, a driving time of the EV driving mode is significantly reduced, which may lead to reduced fuel efficiency.
The above information disclosed in this background section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.